Evidence of latent tuberculosis by purified protein derivative (PPD) screening. PPD screening should be performed according to local standards using the tuberculin skin test (TST). Any result >5mm is considered positive. Prior Bacillus Calmette-Guerin (BCG) should not be taken into account when interpreting a TST result. TST must be performed during the screening period unless one has been performed within the previous 3 months and the results are available.